[Z06] ***Build Date/VIN Analysis of LS6 Valve Spring Failures***
12-01-2012, 07:17 PM
#61
Melting Slicks
Thread Starter
Surely this information exists somewhere, but I wasn't able to find it. If anyone else finds it, please post a link, as it will help to make this study more accurate. I had to estimate these numbers by multiplying the fraction of Corvettes that were Z06's in each model year by the total number of Corvettes built each month.
12-02-2012, 06:04 PM
#62
[QUOTE=skyavonee;1582463342]Surely this information exists somewhere, but I wasn't able to find it. If anyone else finds it, please post a link, as it will help to make this study more accurate. I had to estimate these numbers by multiplying the fraction of Corvettes that were Z06's in each model year by the total number of Corvettes built each month.[/Q
In 2002 there were 35,767 C5s built 8,297 were Z06s (23%). Your info assumes that production every month was 77% C5 & 23% Z06. Your probably pretty close based on the fact that it continued into early 03, but if Z06 production was heavier during the period of 2/02 - 6/02 then the problem may be the same throughout the 02 build rather than just that period. Build per month info is probably hard to find.
In 2002 there were 35,767 C5s built 8,297 were Z06s (23%). Your info assumes that production every month was 77% C5 & 23% Z06. Your probably pretty close based on the fact that it continued into early 03, but if Z06 production was heavier during the period of 2/02 - 6/02 then the problem may be the same throughout the 02 build rather than just that period. Build per month info is probably hard to find.
12-02-2012, 06:54 PM
#63
Melting Slicks
Thread Starter
In 2002 there were 35,767 C5s built 8,297 were Z06s (23%). Your info assumes that production every month was 77% C5 & 23% Z06. Your probably pretty close based on the fact that it continued into early 03, but if Z06 production was heavier during the period of 2/02 - 6/02 then the problem may be the same throughout the 02 build rather than just that period. Build per month info is probably hard to find.
Also recall that it was a pretty big deal when the 2002 Z06 was announced as having 400+ hp. If the build run was lopsided at all, I would expect it to be weighted toward the first half of the year, not the second half, in order to meet demand. But this is just me speculating.
12-07-2012, 09:52 AM
#65
Curious to what your dealership will have to say. Every dealership I have asked about this claims "there is no valve spring problem" DUH.
12-07-2012, 12:52 PM
#66
Melting Slicks
Thread Starter
12-07-2012, 07:24 PM
#67
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the service guy i go to is awesome, he'll probably find it interesting and be surprised, as i have mentioned this to him before. It's the people higher than that you have to worry about blowing it off. The crappy part with my situation is i was replacing the springs in 2 weeks, my spring decided he wanted to go before that though. would have saved me $6000. But now i get a little more torque from boring it out a little and new valve springs before i go to the Autobahn to play with Porsche's and other high end cars on the Autobahn. 
Last edited by bignasty; 12-07-2012 at 07:26 PM. Reason: addition
12-07-2012, 07:33 PM
#68
the service guy i go to is awesome, he'll probably find it interesting and be surprised, as i have mentioned this to him before. It's the people higher than that you have to worry about blowing it off. The crappy part with my situation is i was replacing the springs in 2 weeks, my spring decided he wanted to go before that though. would have saved me $6000. But now i get a little more torque from boring it out a little and new valve springs before i go to the Autobahn to play with Porsche's and other high end cars on the Autobahn.
12-08-2012, 05:34 PM
#70
VIN # shows that you were in the probable group for a valve spring to let go. Hope you have good luck with the new engine.
12-09-2012, 08:19 PM
#71
Did a little more digging and found some build info on the C5 Registry site.
In 2002 48% of the Zs were built in the first half of the year and 52% were built in the second half (345 more built in 2nd half of year).
In 2003 55% of Zs were built in the first half of the year and 45% in the second half (821 more built in 1st half).
Unfortunately, I still can't find a build by month # for Zs but there were more built during the high spring failure months of 02 & 03 than the low spring failure months.
In 2002 48% of the Zs were built in the first half of the year and 52% were built in the second half (345 more built in 2nd half of year).
In 2003 55% of Zs were built in the first half of the year and 45% in the second half (821 more built in 1st half).
Unfortunately, I still can't find a build by month # for Zs but there were more built during the high spring failure months of 02 & 03 than the low spring failure months.
12-09-2012, 08:38 PM
#72
Melting Slicks
Thread Starter
Did a little more digging and found some build info on the C5 Registry site.
In 2002 48% of the Zs were built in the first half of the year and 52% were built in the second half (345 more built in 2nd half of year).
In 2003 55% of Zs were built in the first half of the year and 45% in the second half (821 more built in 1st half).
Unfortunately, I still can't find a build by month # for Zs but there were more built during the high spring failure months of 02 & 03 than the low spring failure months.
In 2002 48% of the Zs were built in the first half of the year and 52% were built in the second half (345 more built in 2nd half of year).
In 2003 55% of Zs were built in the first half of the year and 45% in the second half (821 more built in 1st half).
Unfortunately, I still can't find a build by month # for Zs but there were more built during the high spring failure months of 02 & 03 than the low spring failure months.
12-10-2012, 06:39 PM
#73
Here is the link to the C5 registry build info page.
http://www.c5registry.com/MembersOnlly/production.htm
You can look at builds to mid year and builds for total year from 97-04.
http://www.c5registry.com/MembersOnlly/production.htm
You can look at builds to mid year and builds for total year from 97-04.
12-10-2012, 09:08 PM
#74
Melting Slicks
Thread Starter
Here is the link to the C5 registry build info page.
http://www.c5registry.com/MembersOnlly/production.htm
You can look at builds to mid year and builds for total year from 97-04.
http://www.c5registry.com/MembersOnlly/production.htm
You can look at builds to mid year and builds for total year from 97-04.
12-11-2012, 11:30 PM
#75
Instructor
Help me understand what we are trying to prove hear. It's established there is reason for concern. I just ordered all the parts to do the swap for less than two hundred dollars. It also seems like a nice winter project and the worry is over, move on and quit fretting. How much more convincing could you possibly need?
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12-12-2012, 12:21 PM
#76
Melting Slicks
Thread Starter
Help me understand what we are trying to prove hear. It's established there is reason for concern. I just ordered all the parts to do the swap for less than two hundred dollars. It also seems like a nice winter project and the worry is over, move on and quit fretting. How much more convincing could you possibly need?
The point of this study was to help Z06 owners make an informed decision about changing their valve springs, by gathering all available data and presenting it in a way that is easy for (almost) everyone to understand.
12-24-2012, 02:44 PM
#77
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Just came across this. Fellow 
who bought my Z off a friend early summer.
2003 Z06 42km (or 26ish K miles) last 5 digits of VIN 03940, so I'm assuming I should change the springs as a precaution. I'll be tracking in (road course) 6-8 times a year going forward.
Steve
who bought my Z off a friend early summer.2003 Z06 42km (or 26ish K miles) last 5 digits of VIN 03940, so I'm assuming I should change the springs as a precaution. I'll be tracking in (road course) 6-8 times a year going forward.
Steve
12-24-2012, 04:51 PM
#79
The swap is sooo easy in the big scheme of things and so affordable it should make it an easy decision. Whether or not your are tracking the car or not is fairly irrelevant to the springs breaking. Some have broken at low mileage, some high mileage, others at idle, some at highway speed. No real correlation to actual operation vs. breakage.
12-29-2012, 09:00 PM
#80
Pro Mechanic
Pro Mechanic
I've read this thread with interest and I appreciate the work in gathering the information, but I'm questioning some of the data.
If the issue here is "defective" valve springs, then for this data to be credible, you MUST refuse to consider any spring failures on engines which have been modified with:
1) Calibration with a rev limiter which has been set higher than stock
2) Camshafts having more duration or higher lift.
3) Rocker arms with higher ratios.
Also, you shouldn't consider engines in cars which have been raced frequently in cycles where the engine is often above 5000 rpm or have engine mileages over 60,000.
My guess is if you apply those "rules" the amount of failures is going to be significantly less.
My '04 has higher-ratio rockers and a 6800-rpm rev limit so I swapped the OE springs for Crane dual springs and ti retainers. Had I kept the stock springs, I'd have likely had a spring failure.
If the issue here is "defective" valve springs, then for this data to be credible, you MUST refuse to consider any spring failures on engines which have been modified with:
1) Calibration with a rev limiter which has been set higher than stock
2) Camshafts having more duration or higher lift.
3) Rocker arms with higher ratios.
Also, you shouldn't consider engines in cars which have been raced frequently in cycles where the engine is often above 5000 rpm or have engine mileages over 60,000.
My guess is if you apply those "rules" the amount of failures is going to be significantly less.
My '04 has higher-ratio rockers and a 6800-rpm rev limit so I swapped the OE springs for Crane dual springs and ti retainers. Had I kept the stock springs, I'd have likely had a spring failure.
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